It is well known that an aircraft in flight is commanded through three axes of control, namely the pitch, roll and yaw axes. Control surfaces on the aircraft structure are thus commanded by a pilot (or autopilot if so equipped) to move in appropriate directions so the aircraft attitude may be controllably adjusted relative to such axes of control to thereby allow control over the aircraft's flight path. In conventional aircraft, control of the aircraft about the yaw axis is typically accomplished through foot pedals in the aircraft cockpit which when manipulated by the pilot's feet cause an aircraft rudder to be deflected and thereby yaw the aircraft in the desired direction. Thus, pressing the right rudder pedal will cause the aircraft to yaw rightward while pressing the left rudder pedal will cause the aircraft to yaw leftward.
Movement of the aircraft about the pitch and roll axes is typically accomplished through a control yoke or wheel that is capable of being reciprocally moved forward and aft relative to the aircraft's longitudinal axis as well as being rotated rightward and leftward. Specifically, forward and aftward movement of a control yoke by the pilot will responsively cause an aircraft elevator control surface to be deflected causing downward and upward aircraft pitch changes, respectively. Rotation of the control yoke by the pilot will responsively cause the aircraft's wing-mounted ailerons to be deflected so as to cause rightward and leftward aircraft roll. Therefore, with regard to pitch and roll commands, it is necessary that the movements are separated from each other, even though the pilot command inputs are through a common structural element, the yoke or wheel. Furthermore, since it is necessary for a pilot to provide simultaneous control inputs for all three control axes in order to maintain a coordinated flight attitude, the pitch and roll control system must be capable of pantographic movements.
There are basically two types of control yoke arrangements in conventional aircraft. The first type (e.g., so-called column systems) includes an upright column which is moveable forward and aft so as to control aircraft pitch movement. A yoke is rotatably mounted to the upper end of the column so as to allow for commanded right and left aircraft roll movements in response to turning the yoke right and left, respectively.
A second type of control yoke arrangement (e.g., so-called axial systems) involves a yoke which is installed at an aft end of a yoke shaft which is aligned generally axially with respect to the aircraft. According to one conventional solution, the yoke shaft is composed of a pair or telescopic shafts with the external shaft having a circular cross-section and the internal shaft having a square cross-section. The external shaft is connected rigidly to the yoke at its aft end and includes at its opposite end a sleeve arm installed with bearings to discard rotational movement and instead only allow longitudinal movements to be transmitted to the elevator control system. The internal shaft on the other hand is supported by rollers of the external shaft so as to allow rotational movement of the external shaft to be transmitted to the aileron control quadrants.
While a variety of pitch and roll control systems are already known in the art, some improvements are still desired. For example, it would especially be desirable if an axial control system could be provided such that pitch and roll commands are separated from one another using a single control shaft connected to the yoke. Such an arrangement would thereby reduce the complexity of the control system thereby potentially leading to reduced manufacturing and/or maintenance costs. It is therefore towards fulfilling such needs that the present subject matter is directed.